System and method for demagnetization of a magnetic structure region

• US 9,275,783 B2
• Filed: 10/14/2013
• Issued: 03/01/2016
• Est. Priority Date: 10/15/2012
• Status: Expired due to Fees

• Current Assignee: Correlated Magnetics Research, LLC
• Original Assignee: Correlated Magnetics Research, LLC
• Inventors: Fullerton, Larry W., Roberts, Mark D., Moore, Hamilton Grant
• Primary Examiner(s): Musleh, Mohamad
• Application Number:
  US14/052,891
• Publication Number:
  US 20140104021A1
• Time in Patent Office: 869 Days
• Field of Search: 336/223, 336/232, 335284-295, 335/299
• US Class Current: 1/1
• CPC Class Codes: H01F 13/006 Methods and devices for demagnetising of magnetic bodies, e.g. workpieces, sheet material for erasing of information on magnetic record carriers G11B5/00

Abstract

A system and a method are described herein for demagnetizing a region of a magnetic structure. In one embodiment, the system comprises: (a) a pulsed magnetizer; and (b) at least one magnetizing coil that receives a sequence of discrete current with continually decreasing current values from the pulsed magnetizer and outputs a sequence of discrete magnetizing fields with continually decreasing field strengths to overwrite and at least partly demagnetize the region of the magnetic structure. The at least one magnetizing coil is located adjacent to the region of the magnetic structure.

Claims

1. A system for demagnetizing a region of a magnetic structure, the system comprising:

a pulsed magnetizer; and

at least one magnetizing coil that receives a sequence of discrete current pulses with continually decreasing current values from the pulsed magnetizer and outputs a sequence of discrete magnetizing fields with continually decreasing field strengths to at least partly demagnetize the region of the magnetic structure, wherein the region is one of a plurality of regions of the magnetic structure, wherein the magnetic structure comprises a permanent magnet material previously magnetized such that a plurality of magnetic sources are exposed on a surface of said magnetic structure including at least one first magnetic source having a first polarity and at least one second magnetic source having a second polarity opposite said first polarity, wherein the sequence of discrete current pulses and the sequence of discrete magnetizing fields correspond to a sequence of discrete magnetizing events, and wherein the at least one magnetizing coil is located adjacent to the region on the surface of the magnetic structure during said sequence of discrete magnetizing events, and wherein after said region is at least partly demagnetized at least one other region of said plurality of regions of said magnetic structure remains as previously magnetized.

2. The system of claim 1, wherein the at least one magnetizing coil receives the sequence of discrete current pulses with continually decreasing current values from the pulsed magnetizer and outputs the sequence of discrete magnetizing fields with the continually decreasing field strengths and alternating polarities to at least partly demagnetize the region of the magnetic structure.

3. The system of claim 1, wherein the at least one magnetizing coil receives the sequence of discrete current pulses with continually decreasing current values from the pulsed magnetizer and outputs a first portion of the sequence of discrete magnetizing fields with the continually decreasing field strengths and a first polarity and then outputs a second portion of the sequence of discrete magnetizing fields with the continually decreasing field strengths and a second polarity to overwrite and at least partly demagnetize the region of the magnetic structure.

4. The system of claim 1, wherein the first magnetic source comprises at least one maxel having the first polarity.

5. The system of claim 4, wherein each maxel has a size, shape, depth, polarity, field strength, and angle relative to the surface of the magnetic structure.

6. The system of claim 1, wherein each magnetizing coil has a metal type, layer thickness, number of turns, aperture width, coil width, coil shape, and aperture shape.

7. The system of claim 1, wherein the continually decreasing field strengths decrease with a predetermined decrement pattern.

8. The system of claim 1, wherein the continually decreasing field strengths have a starting field strength selected based on a field strength of the region of the magnetic structure as determined prior to demagnetization.

9. The system of claim 8, wherein the starting field strength is lower than the field strength of the region of the magnetic structure as determined prior to demagnetization.

10. The system of claim 1, wherein the continually decreasing field strengths have a starting field strength selected based on characteristics of the permanent magnet material.

11. The system of claim 1, wherein the at least one magnetizing coil is at least one movable magnetizing coil.

12. A method for demagnetizing a region of a magnetic structure, the method comprising:

generating, by a pulsed magnetizer, a sequence of discrete current pulses with continually decreasing current values;

receiving, by at least one magnetizing coil, the sequence of discrete current pulses with continually decreasing current values; and

outputting, by the at least one magnetizing coil, a sequence of discrete magnetizing fields with continually decreasing field strengths to at least partly demagnetize the region of the magnetic structure, wherein the region is one of a plurality of regions of the magnetic structure, wherein the magnetic structure comprises a permanent magnet material previously magnetized such that a plurality of magnetic sources are exposed on a surface of said magnetic structure including at least one first magnetic source having a first polarity and at least one second magnetic source having a second polarity opposite said first polarity, wherein the sequence of discrete current pulses and the sequence of discrete magnetizing fields correspond to a sequence of discrete magnetizing events, and wherein the at least one magnetizing coil is located adjacent to the region on the surface of the magnetic structure during said sequence of discrete magnetizing events, and wherein after said region is at least partly demagnetized at least one other region of said plurality of regions of said magnetic structure remains as previously magnetized.

13. The method of claim 12, wherein the at least one magnetizing coil receives the sequence of discrete current pulses with continually decreasing current values from the pulsed magnetizer and outputs the sequence of discrete magnetizing fields with the continually decreasing field strengths and alternating polarities to at least partly demagnetize the region of the magnetic structure.

14. The method of claim 12, wherein the at least one magnetizing coil receives the sequence of discrete current pulses with continually decreasing current values from the pulsed magnetizer and outputs a first portion of the sequence of discrete magnetizing fields with the continually decreasing field strengths and a first polarity and then outputs a second portion of the sequence of discrete magnetizing fields with the continually decreasing field strengths and a second polarity to overwrite and at least partly demagnetize the region of the magnetic structure.

15. The method of claim 12, wherein the first magnetic source comprises at least one maxel having a first polarity.

16. The method of claim 15, wherein each maxel has a size, shape, depth, polarity, field strength, and angle relative to the surface of the magnetic structure.

17. The method of claim 12, wherein each magnetizing coil has a metal type, layer thickness, number of turns, aperture width, coil width, coil shape, and aperture shape.

18. The method of claim 12, wherein the continually decreasing field strengths decrease with a predetermined decrement pattern.

19. The method of claim 12, wherein the continually decreasing field strengths have a starting field strength selected based on a field strength of the region of the magnetic structure as determined prior to demagnetization.

20. The method of claim 19, wherein the starting field strength is lower than the field strength of the region of the magnetic structure as determined prior to demagnetization.

21. The method of claim 12, wherein the continually decreasing field strengths have a starting field strength selected based on characteristics of the permanent magnet material.

22. The method of claim 12, wherein the at least one magnetizing coil is at least one movable magnetizing coil.